Women have been more systematically excluded from doing serious work in science than from doing any other social activity except, perhaps, military combat. Given the many discriminatory barriers women have faced and the fact that women have frequently been ignored, robbed of credit, or forgotten when they have made important contributions to the sciences, it is not surprising that few women have been able to achieve eminence as scientists. The factors that account for the past suppression of women's voices in science are multifaceted, but because of the cognitive authority granted to science, none have been more pernicious or self-reinforcing than the theories scientists have produced (in the absence of women) about women's supposed intellectual inferiority.

The first systematic, scientific explanation of woman's intellectual inferiority can be traced back to >>Aristotle<<, whose theory that a defect in generative heat impairs female brain development influenced scientific thinking well into the eighteenth century. In the late 1700s, scientific views of sex and gender differences began to shift from a hierarchical model, in which woman was conceptualized as a defective man, to a model of complementary differences, which depicted woman as man's opposite and as perfect in her own way.

For women, unfortunately, this advance in thinking was more apparent than real. Because of the centuries-old tradition within Western intellectual thought of defining difference in terms of privation, the very characteristics presumed to make up woman's difference were perceived as having a lower degree of perfection than those of man. For example, emotion—one of woman's ascribed "perfections"—was characterized as resulting from the lack of rational control of the passions. Because of this defect in rational control, women's emotionality was also taken to be a mark of her inferiority and a reason to continue excluding members of her kind from science.

The alleged defect in women's minds that supposedly prevents women from excelling in science has changed over time—for example, from inadequate heat to inferior skull size, hormone deficiencies, and brain lateralization peculiarities. Because women have been defined out of science since ancient times, the question of women's real place in science is often approached by scholars as a matter of documenting the accomplishments of women scientists. Much of this work employs the "great man" approach to history, with the focus on women instead of men.

This approach has its difficulties: distinguished male scientists outnumber distinguished female scientists by a wide margin, and emphasizing "great women" does little to reveal the more usual patterns of women working in science. Even more problematically, perhaps, the focus on exceptional women scientists retains the norms and modalities traditionally associated with masculinity as the standard of excellence. This mode of doing history measures women's contributions to science against what men of European descent have valued and defined as science; and it tends to hide the racialized identities of women scientists, what the work of women scientists has meant to different populations of women and men, and how this work has underwritten and shaped elite men's very definition of science.

If the focus is shifted from recounting the stories of exceptional women scientists to examining the interplay between the social barriers to women's advancement in science and the strategies women have employed to secure a place in science, a more adequate picture of women's participation in science emerges. The vast majority of American women scientists in the modern era have been marginalized and underutilized, not for the lack of talent, hard work, or ability to seize enhanced opportunities, but because of what Margaret Rossiter has called hierarchical and territorial forms of occupational sex segregation.

Hierarchical discrimination has shaped women's participation in science by channeling them into auxiliary, low-status, low-paying positions, for example, as assistants in museums, "invisible" partners in husband-wife teams, technicians in industrial laboratories, educators in high schools, instructors in colleges, and scientific editors. The experiences of American women in astronomy in the late 1800s and early 1900s provide a vivid example of this type of occupational segregation.

Around the turn of the century in the United States, astronomy was experiencing rapid growth as larger observatories and bigger telescopes were being built, and new problematics, theories, methodologies, and techniques were being developed. For socially privileged women, these changes meant increased opportunities for employment. At the older observatories, women were offered some of the work once performed by male assistants, who now had new, exciting possibilities elsewhere. New technology such as spectrophotography created an increased need for cheap, intelligent labor. The type of work engendered by this technology—classifying, cataloging, and computing that required painstaking attention to detail—was easily categorized as "women's work."

Sex typing, however, was a mixed blessing, and it was a dynamic that operated primarily for socially advantaged women, since women belonging to racial and ethnic minorities were largely excluded from even the bottom rungs of the profession. While providing a place in the field for socially privileged women, the feminization of specific jobs within astronomy meant that the "lucky" few were confined to spheres of activity that afforded few opportunities for advancement, salary increases, or personal challenge. Because they worked essentially as "organic computers" under the control of observatory directors, the work they were assigned was not regarded as requiring much original or theoretical thinking. While women who secured positions in observatories were invariably indebted to the progressive attitudes of individual male directors, their participation in astronomy was nevertheless mediated by men, who were still subject to prevailing gender stereotypes and who, as project directors, received most of the credit for published work.

The alternative employment setting for women astronomers in the United States—the newly created women's colleges in the North—afforded some women more opportunities to undertake independent research. But because of heavy teaching loads and administrative responsibilities, poor funding for basic equipment, and external and internal pressure to pursue feminized research topics, women professors were not able to escape sex typing and sex segregation. This is not to say that women professors were unsuccessful at research. As with their counterparts in the observatories, despite considerable gender-specific barriers, they helped to advance their field, especially by contributing to the steady accumulation of small-scale discoveries, but also by making conceptual innovations.

The need for cheap labor was probably the engine driving the practice of sex segregation in astronomy; gender ideology simply provided the rationalization for this practice. Whereas certain types of work or roles within astronomy became feminized because they were low-paying and low-status, in other scientific arenas whole fields (e.g., home economics, nutrition, nursing) and entire specialties within fields were sex-typed as being inherently feminine and, therefore, the most suitable locations for aspiring women scientists. Psychology's evolution into the sex-segregated areas of theoretical science (male) and applied professional activities (female) illustrates this latter phenomenon of territorial discrimination.

In the early twentieth century, problems resulting from industrialization (e.g., poverty, overcrowding, child labor) created a somewhat expanded area of professional practice for women, especially for socially privileged women, but gradually also for women belonging to racial and ethnic minorities. Training institutes and psychological clinics were work settings that neither violated society's assumptions about "women's natural place" nor challenged the cultural assumption that women are too mired in the immediate and practical to apprehend the abstract and universal. Applied psychology quickly became identified and devalued as "women's work," and despite tremendous contributions by women psychologists to the growing fields of child development and education (as well as other related fields), by World War I a kind of territorial ghetto for women psychologists was firmly established.

During World War II, the military's need for psychological expertise in recruitment, training, psychometrics, and human factors research greatly stimulated the growth of traditionally male-dominated subfields. While women psychologists were often expected to volunteer their services to tend the "home fires" in the civilian population, men's "war work" achieved a status that was prestigious, highly paid, and decidedly "masculine" in the sense of being regarded as rigorous, objective, impersonal, tough, competitive, and unemotional. Masculinized subfields such as industrial psychology, psychometrics, and comparative and experimental psychology continued to flourish after World War II as increased educational opportunities and a restored confidence in science drove a greater wedge between "true" scientific psychology and its "distant" feminine relatives. To this day, the masculinized subfields of psychology enjoy a greater degree of scientific respectability than do the feminized ones—a fact that would seem to reflect the ways in which the dialectic between ideologies of gender and science has shaped the social construction of gender and science.

What the examples of astronomy and psychology show is that while gender stereotypes enabled women to acquire a niche in science, they also locked women into a pattern of sex-segregated employment and underrecognition. This helped perpetuate the ideology of gender difference, and because of the racist and ethnocentric dimensions of the sexual division of labor, women belonging to racial and ethnic minorities were left stranded on the most distant perimeters of science.

In the late 1990s, significantly greater numbers and populations of women are undertaking graduate studies in every field of science and are working at every level in all scientific disciplines and employment sectors. As promising as these developments may seem, women still experience salary inequities at all levels, lower rates of tenure and promotion in academe, restricted opportunities for career advancement in nonacademic employment sectors, higher rates of schooling and employment in feminized fields, and greater levels of involuntary unemployment, part-time employment, employment out-of-field, and underemployment. At the same time, there continue to be subtle, but troubling, replays of the age-old notion that innate differences between the thinking of women and men preclude women from excelling in science.

Women's historical confinement to the periphery of science does raise important questions about gender and science. Is the past suppression of women's voices in science simply a matter of mistaken or irrational social differentiation? Have gender-based patterns of exclusion distorted the content, methods, norms, or practices of science? What are the limits, if any, of fighting sexist science with science in its present form? Full gender equity has proved elusive in science. For many feminists, the question about what should be done to improve the situation of women in science is also a question about how to expand the meaning of science.